The present invention relates to a gas or fuel-tank cap. More particularly this invention concerns a fuel-tank filler assembly for a motor vehicle.
A fuel tank, for instance on a motor vehicle, has a filler tube whose outer end is normally closed by a cap that is removed for insertion of a filling nozzle when the tank is to be refilled. In order to suppress release of vapors from the tank, which is typically connected via a vent line to the intake manifold of the vehicle engine, the cap must make a very tight seal.
Thus it is standard for the cap to have a tubular center part that fits down into the filler tube and that has an outer surface confronting an inner surface of the tube. One of these surfaces, normally the outer surface of the cap""s center part or an inner face of the cap, is provided with a compressible seal that presses radially or axially against the other surface when the cap is secured in place, which is normally assisted by some sort of bayonet or screwthread system. See for example U.S. Pat. No. 2,597,014 of Mariani, U.S. Pat. No. 6,220,064 of Oddenino, or French patent 2,627,748 of Percebois.
The disadvantage of these arrangements is that insertion of the normally metallic filler nozzle into the filler tube entails some scraping of the nozzle on the inner filler-tube surface or at least one of the seal surfaces is left exposed when the cap is removed. The result is some scratching and scoring of this filler-tube surface. In time the damage is such that a good seal can no longer be made against the filler-tube surface. In fact in old cars as much as 80% of the vapors that escape from the vehicle do so via the faulty filler-tube seal.
It is therefore an object of the present invention to provide an improved filler-tube assembly for a fuel tank.
Another object is the provision of such an improved filler-tube assembly for a fuel tank which overcomes the above-given disadvantages, that is which ensures that a good seal will be maintained over a long service life.
A filler-tube assembly for a fuel tank has according to the invention a filler tube having an upper end formed by a tubular inner wall defining a fill passage and having an outer surface and a concentric outer wall fixed relative to and defining with the inner wall an annular and upwardly open space and having an inner surface and an end surface. A cap adapted to fit over the outer end has a tubular extension fittable in the space and having inner and outer surfaces and an end surface bridging the respective inner and outer surfaces. A seal ring in the space is engaged between one of the surfaces of the cap and one of the surfaces of the filler tube.
Thus with this arrangement the inner tube shields the seal surfaces so that a nozzle inserted into the passage cannot scratch and mar them. The seal ring will be able to form a perfect seal in the long run, completely preventing vapors from leaking out of the tank past the cap.
According to the invention the inner and outer walls have generally coplanar upper edges. Thus the seal surfaces are effectively recessed out of the way, well below the plane of these upper edges.
Furthermore the cap has an annular outer lip engaging downward around the outer wall. This outer lip and the outer wall are formed with complementary screwthread formations.
The seal ring in accordance with the invention can be set in the tubular cap extension and radially outwardly engage the inner surface of the outer wall. Alternately the seal is engaged between the end surfaces of the cap and filler tube.
The outer wall according to the invention is formed between the respective inner and end surfaces with an upwardly directed bevel. Similarly, the inner wall is formed at an outer edge of the respective inner surface with an upwardly directed bevel.
The fill tube can be formed with a second outer wall spaced radially outward from the first-mentioned outer wall and forming therewith an upwardly open annular space. The cap is formed with an outer lip fittable downward into the space between the second outer wall and the first outer wall. In addition the fill tube is formed at a base of the space between the second and first outer walls with a drain hole. In the same manner the fill tube is formed at a base of the space between the inner and outer walls with a drain hole opening into the passage. Thus any fuel that gets into the inner space when the cap is removed will be diverted down to the tank while any other liquid flowing over the cap into the outer space will be diverted outward.